This invention relates to magnetic imaging; and, more particularly, to development apparatus suitable for the high speed development of latent magnetic images with magnetic toner.
Latent magnetic images on magnetizable imaging members are typically developed by deposition of magnetic developer material commonly referred to as magnetic toner onto the magnetizable imaging member. The developing material is attracted to the magnetizable member by magnetic fields constituting the latent magnetic image.
However, in developing latent magnetic images on a magnetizable member, it is necessary to introduce the developing material within a very short distance from the latent magnetic image, typically within about 10 microns of the image, due to the short range nature of the magnetic forces associated with the latent magnetic image. Accordingly, flood contact development of latent magnetic images is generally preferred as a technique which will ensure that the magnetic toner material is introduced within the short distance from a latent magnetic image to allow full, dense development. Moreover, high speed development involving applying magnetic toner to a magnetic tape moving through its path of travel through the developer zone at a high rate of speed such as, for example, 100 inches per second or greater, invariably produces powder clouds of airborne toner. These powder clouds of airborne toner are quite troublesome, if not controlled, resulting in the probable redeposition of magnetic toner on areas of the developed image where magnetic toner is not desired and generally results in a dirty interior of the magnetic imaging device.